Embodiments presented herein relate generally to electronic circuit board assemblies, and more specifically to an electronic circuit board capable of high temperature operation and a related method thereof.
A printed circuit board (referred to as “PCB”) is often used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces that may be etched from metal sheets laminated onto a non-conductive substrate. A PCB populated with electronic components is a printed circuit assembly and may also be referred to as a printed circuit board assembly (PCBA).
Conventional conducting layers of the PCB are typically made of thin copper foil. The vast majority of printed circuit boards are made by bonding a layer of copper over the entire substrate, sometimes on both sides, then removing unwanted copper in a subtractive processing technique after applying a temporary mask (e.g. by etching), leaving only the desired copper traces. Some PCBs are made by adding traces to the bare substrate, in an additive processing technique, usually by multiple electroplating steps. The copper material commonly used for these conducting traces has low resistivity and costs, but easily oxidizes with a resultant increase in resistance, which decreases its reliability. In addition, this type of conventional PCB may be limited to applications at a temperature below 200 degrees Celsius.
High temperature PCBs typically use noble metals to form the traces, or conductors, on ceramic substrates to interconnect circuit elements. More particularly, many high temperature (above 200 degrees Celsius) operation PCBs use thick film gold (Au) or silver (Ag) films. These types of films are used due to their inherent low resistivity and minimal oxidation. However, these precious metals are expensive to use. Thin films of gold (Au) or silver (Ag) have been used, however they require sufficient barrier and adhesion layers to prevent intermixing with the precious metal at high temperature.
Irrespective of the operating temperature, after the PCB is completed, electronic components are attached to form a functional printed circuit assembly. In a surface-mount technique, the components are placed on pads on the outer surfaces of the PCB and in electrical contact with the conductive traces. The component leads may be electrically and mechanically fixed to the board with a molten metal solder.
In light of the above, it is desired to provide an improved electronic circuit device capable of withstanding high temperature operations, while maintaining low cost manufacture.